Digital sound compression.
Principle and method of digital audio compression.
Audio data compression is a process of lowering the bit rate by reducing the statistical and psychoacoustic redundancy of the digital loop signal. Methods for reducing the statistical redundancy of audio data are also called lossless compression, and consequently methods for reducing psychoacoustic redundancy are called lossy compression. Lossless compression The reduction of statistical redundancy is based on consideration of the properties of the audio signals themselves. It is determined by the presence of a correlation between adjacent samples of a digital audio signal, the elimination of which allows the amount of transmitted data to be reduced by 15 … 25% compared to its original value. To transmit a signal, you need to obtain a more compact representation of it, which can be achieved with the help of orthogonal transformation. Important conditions for the application of such a transformation method are: the ability to restore the original signal without distortion. the ability to provide the highest energy concentration in a small number of conversion factors. fast computational algorithm
Lossy compression Lossy compression of audio data is based on the imperfection of the human ear in the perception of audio information. The inability of a person in certain cases to distinguish between silent sounds in the presence of louder sounds, called the masking effect, has been used in algorithms to reduce psychoacoustic redundancy. The auditory masking effects can be divided into two main groups: frequency masking (simultaneous). Temporal (non-simultaneous) masking The masking effect in the frequency domain is associated with the fact that, in the presence of large amplitudes of sound, the human ear is insensitive to small amplitudes of nearby frequencies.
24. Analog and digital video signals. Hardware for digital video recording (digital cameras).
A video signal is usually a low-frequency signal, the value of which itself carries information. For example, it controls the strength of an electron beam in a cathode ray tube on a television. The beam “runs” across the screen and changes its value (according to the law, which is set by the video signal) – as a result, you get a frame.
Analog video signal
Analog television: Television produced by analog signals whose magnitude changes continuously over time. Today’s television system uses magnetic waves to transmit and display images and sound.
Digital video signal
Digital television is a method of transmitting and receiving compressed MPEG-2 digital video signals. Simply put, it is a modern replacement for traditional analog television, allowing you to transmit and receive television programs in greater quantities at the same costs and in much higher “digital” quality (as opposed to analog television, where the quality of television programs depends on the level of the received signal and the signal-to-noise ratio, in digital television, the quality of television programs does not change and is initially high.If the received signal exceeds a certain threshold level for open a digital package of television programs, then the programs are displayed with a constant quality that depends only on the quality of the original video material and the bitrate chosen by the broadcaster to broadcast a specific TV program). ..
Digital video cameras.
“What is the difference between digital and analog video cameras?
+ Let’s start by listing the most important advantages of a digital video camera in our opinion. First of all, digital video cameras deliver such excellent image quality that you could hardly have dreamed of more. Also, multiple copies are possible, and each subsequent copy is no worse than the first. In addition, it is important that from the moment of filming until the moment of watching your film, a minimum of time passes, and if you want to print a photo from a separate frame, then if you have a computer and a color printer (which is not necessary, as such services are also provided in classrooms) It only takes a few minutes. The quality of photos taken this way is very high (this, of course, is determined by the quality of your camera).
